Sunday, April 22, 2012

A biological refugium

Well, we’re recently back from McGill’s spring CEEB (Conservation, Ecology, Evolution, and Behavior) retreat, which was a blast.  It was held at McGill’s field station at Mont St-Hilaire:



 That’s Lac Hertel, the lake that is rather curiously perched in the middle of the ring of hills that comprises the “Mont”.  (It rather looks like a volcanic caldera lake, but that is not the case; the Monteregian Hills are igneous intrusions, not extinct volcanoes, and the lake was formed by glacial erosion.)  The Gault House where the retreat was held is the building visible on the lake shore.  Nice digs.

  Below, Krista Oke and Shahin Muttalib write a bit about the research they presented at the retreat; but first, trivia!  These questions were prepared by Gregor Fussman to test the wits of the assembled graduate students.  Answers are at the bottom of the post.

Question 1. What happened in which year?  (Match each lettered year with one of the listed events.)

a) 1821, b) 1822, c) 1831, d) 1851

Events:

“Moby-Dick” published
McGill University founded
Hieroglyphs on the Rosetta Stone deciphered
Voyage of the Beagle starts

                    Profs and students are stumped by the trivia

  Question 2. Whose equation?  (Match each lettered equation to its author.)


a)                        


b) 


c)  


d) 

 Authors:

W. D. Hamilton (1964)
C. S. Holling (1959)
Richard Levins (1969)
Russ Lande (1976)

Question 3. The Latin name of which plant (which you would correctly assume that we consumed that evening) contains the letter ‘u’ six times, and contains no other vowels?

Question 4. The path of this traveller is suggestive of what?


Question 5. Rank these bodies of water according to their actual area, from largest to smallest.

a) 

b)

c)

d)







 ____________________________
Shahin Muttalib
The balance between selection and gene flow evaluated in threespine stickleback

The degree to which gene flow can constrain adaptation is still an open question, and inferring causality from correlation studies between levels of divergence and levels of gene flow isn’t quite convincing enough.  Another approach is to measure selection in a site where we expect to find maladaptation: maladapted populations should experience higher selection. With this in mind, I tagged hundreds of fish over two winters and two summers in Misty Outlet and Misty Inlet, hoping to estimate natural selection on body shape. Since good selection estimates are dependent on capturing as many surviving fish as possible, I first estimated survival and recapture probability. It turns out recapture probability was higher in the outlet, so selection estimates are more precise for the outlet. Survival probability was lowest in the winter in the outlet, which is also where I found the highest selection intensity.  I am using two metrics to measure total selection intensity: one for overall selection due to the traits that I have measured, and a measure of relative selection taking into account selection on unmeasured traits. So while the outlet has higher overall selection in the winter, it also has more selection due to other traits. At the level of particular traits, I have found effects for fin positioning, head size, body depth and position of the pelvic spine. These are traits that contribute most to total selection intensity, show the strongest selection gradients, and also show selection in the expected direction, i.e.: towards the more adapted inlet trait values. This spring the stickleback team will be wading through the streams for one last season of data to confirm if selection is indeed consistently higher over the winter in the outlet. Watch out for those Misty Lake zombies!

____________________________

 Krista Oke
An investigation into the genetic versus plastic basis of parallel evolution in lake and stream stickleback

The study of parallel evolution is important because it provides evidence for a deterministic role of natural selection in evolution and speciation, but parallel evolution is much more often inferred from field studies. Laboratory studies on parallelism have been relatively rare. Since plasticity could affect parallelism in several ways, the use of common garden studies could provide much insight into this process. A genetic basis for parallelism has been detected in some traits in one lake-stream stickleback pair, the Misty Lake pair, although plasticity was also detected. My MSc work asks whether there is a genetic or plastic basis to parallel evolution in three other watersheds on Vancouver Island. I currently have first generation lab fish growing in a common garden setup in our lab at McGill, but so far no results to report. I will be part of the field crew Shahin mentioned heading back to BC soon, where we will also be creating crosses to supplement the fish I have in the lab now. No one warned me about the zombies, though!

                          Krista giving her talk on parallel evolution


 Trivia Answers

Question 1: a) McGill, b) Rosetta Stone, c) the Beagle, d) Moby-Dick
Question 2: a) Hamilton, b) Levins, c) Lande, d) Holling
Question 3: Humulus lupulus (hops)
Question 4: the sites of the last five annual ESA meetings
Question 5: c (Caspian Sea), b (Lake Superior), a (Lake Baikal), d (Great Slave Lake)

If you now have the warm, triumphant glow of a life spent immersed in the companionship of friends who love biology – but you also have a hangover and are in desperate need of a shower – then this post has given you a taste of what the CEEB retreat is like. Hey, at least we didn’t bring up meme-sex this time!

BUT, the trivia wasn’t quite over. A surprise last question moved the team rankings around, so a final challenge was issued. It was a combination of physical speed (running around the building twice), teamwork, memorization, and knowledge of your field. What was most interesting about it was that the team of the person running had to come up with a canonical paper in the field of ecology and evolution. The team would whisper it to the runner, and then they had to write it on a blackboard. This was all fine and good, but several interesting things came out:

1) We all know the authors and years, but do you know the exact title of papers that are important in your field?

2) Do you know which ones are books, and which ones are articles?

3) How do you weigh the relative importance of different papers?

4) Did you know that marker caps, manipulated with excessive haste, can cause wounds?

It was an interesting and contentious final round. Of the articles the teams came up with, the citation counts for the articles ranged from 6 (Hendry and Gonzalez – Whither adaption?) to 12,528 (Fisher – The genetical theory of natural selection). Fisher’s ought to have been eliminated because it is a book, not an article, but that felt like too large a penalty, so the top two teams ended up splitting the prize: a bottle of rare Hendry wine.

Food for thought: at what point does an article become canonical or seminal in your field, and how might this be measured? H-index of the authors? Average citations per year? Total citations? First author awesomeness?

Until next year... hopefully our livers (and our marker-cap-inflicted wounds) will heal by then!

Cheers,

Ben, Kiyoko, Krista and Shahin (Hendry Lab)

PS. Kiyoko apologizes for the publishing, subsequent dissapearance, and then reappearance of the post. In an attempt to add pictures, she managed to edit the draft to nothing. After much teeth gnashing, luck, and hair pulling, she realized Blogger plays nicest with Chrome. She should have known like begets like. Thanks to those who never close their browser windows and were able to send Kiyoko the text so she could ressurect this post. I think the original post has gone to hang out with the Misty Lake zombies. What fun!




Wednesday, April 18, 2012

Convergent performance in divergent environments

            We all know how important oxygen is for us to survive. No oxygen, we’d suffocate. The same is true when considering dissolved oxygen (DO) levels in water. Fish need the oxygen, just as we do, and if there is less DO for them to uptake through their gills, the fish will have to compensate somehow. Think how the air is thinner at higher altitudes – there is less oxygen per unit of air. Humans who live in high altitude areas have adapted to this problem by developing larger lungs allowing for increased uptake of air, and thus, allows the human body to receive the amount of oxygen it needs. As we’ll see, some fish have come up with a similar adaptation to be able to survive in low DO conditions.
                                              Mt. Everest

            Low oxygen areas, or hypoxic waters, occur both naturally and artificially. They occur naturally in areas where there is little photosynthesis, such as the dense papyrus swamps of Eastern Africa. However, hypoxia (and anoxia – no oxygen) is becoming a larger and larger problem, due to humans inputting pollutants in the water system. Eutrophication and ‘dead zones’ are becoming larger and occurring more often and in more places, and can cause massive fish kills, which can devastate industry and the community, especially those dependent on fish as their main source of protein. Interestingly, hypoxic waters can also serve as a refuge. If you’re a low-DO tolerant fish, and your predator isn’t, then you’ve got a place to hang out where you know you won’t get eaten. Not a bad place to hide if you can survive the low DO conditions.
                                                   Fish Kill

                                                   Papyrus Swamp

            So the question then becomes, why are some fish species tolerant and others not tolerant? One adaptation that a particular type of East African cichlid, Pseudocrenilabrus multicolor, employs is to grow larger gills. The larger gills also mean different body morphologies. These fish, when reared under low DO, have larger gills, deeper bodies, and larger heads. But larger gills seem advantageous: why not have big gills all the time? There must be a trade-off of some type that would maintain smaller gills in high-DO conditions.

            To explore this, we decided to measure swimming performance in P. multicolor. Body shape is critical in swimming performance, so perhaps this can give us an insight into what is maintaining the divergent body shape adaptations between different DO levels. We measured two types of swimming performance: critical swimming speed and fast-start swimming. Critical swimming speed (Ucrit) is a measure of sustained swimming ability. Basically, it’d be like running on a treadmill, with the speed increasing at regular time intervals, until you couldn’t run anymore. Fast-start swimming, or burst swimming, or startle response is a response used to evade predators or to catch prey. It’s characterized by rapid acceleration from what is called a C-start where the fish body bends into a C shape. Both types of swimming performance are affected by body shape, so we expected a difference in swimming performance between different morphologies in P. multicolor.

                                             P. multicolor

            To do this, used a split brood design and reared the fish under high and low DO conditions. We know that the fish have different morphologies, so we expected a difference in swimming performance between the rearing conditions of the fish. To our surprise, there was no difference in performance for either Ucrit or fast-start swimming. We know the morphologies were different, so how could fish with bigger gills and fatter heads swim just as well as more stream lined fish?
                                              Split Brood Design

            For fast start swimming, it appears the low DO reared fish, with fatter heads and bigger gills, use what we call a double bend response. After a fish bends into the initial C-shape, the fish might either straighten out and go into sustained swimming, or it might engage in a reverse flip after the initial C-start. When it engages in that reverse flip, it is called a double bend, and double bend responses have high velocity and acceleration. Low DO reared fish engaged more often in a double bend than their high DO reared counter parts. Thus, we think low-DO reared fish compensate for the larger gills and fatter heads by engaging in that second flip to gain more speed in their fast-start swimming response. However, this could be a potential energetic cost, as the we expect that double bend responses are more energetically costly than single bend responses. This might explain why it's not always good to have larger gills - to compensate for the different body shape, fish have to invest more energy in their fast start performance to achieve the same performance as fish with smaller gills. For Ucrit, we think the larger gills might act as better ‘engines’ for the fish, so the increased gill surface area allows for enough oxygen uptake so low-DO reared fish can swim comparably to high-DO reared fish.

            We had expected differences in the swimming performance between high and low DO reared fish, and to our surprise, the fish had converging performance, even though they were from divergent environments. 

Monday, April 2, 2012

Carnival #46: The Tree (Structures) of Life

Another month has already flown, and the 46th Carnival of Evolution is posted at Synthetic Daisies. Our contribution is Felipe PĂ©rez Jvostov’s recent post on Parasites, guppies, and predation; give it a read if you missed it!

Since this Carnival has a tree theme, here’s a photo of my favorite kind of tree, the Joshua tree:

Photo credit: Ben Haller, 2004.